A2 Respiration test
Total marks [40]
The diagram below shows some of the stages in glycolysis:
Glucose
X
Hexose phosphate
X
Hexose biphosphate
Triose phosphate
Y
Pyruvate
Z
Reduced Z
in the cytoplasm
State precisely where this process occurs ………………………………………[1]
ATP/phosphate group from ATP
Identify substance X ……………………………………………..…………………[1]
hydrogen
Identify substance Y ………………………………………………………………..[1]
Briefly outline the fate of substance ‘reduced Z’ …………………………………
…………………………………………………………………………………..
……
Enters mitochondria; is (re-)oxidised; in the electron transport chain;
………………………………………………………………………………………..[2]
Carefully read the following account of aerobic
respiration and then fill in the blanks:
cytoplasm
In the first stages of respiration which occurs in the ………………………………………..
of the cell,
glucose is ………………………………..
to pyruvic acid. Glycolysis yields ………………………….
oxidised
ATP
and a reduced coenzyme.
acetyl CoA
The pyruvic acid then combines with coenzyme A to form ……………………………………..
which
enters the Kreb’s cycle which occurs in the ………………………………………….
of the
matrix
………………………………………………..
mitochondria
During these reactions hydrogen atoms are removed from a series of intermediate compounds by
enzymes called ……………………………………
dehydrogenases . The hydrogen atoms are passed to carriers such as
………………………………………
.
NAD/FAD
oxidised
In the third stage of aerobic respiration, the carriers are alternately reduced and …………………….
electrons
as they gain and lose ………………………….
. Energy is released and used to phosphorylate ADP,
forming ……………………….
. The hydrogen atoms finally combine with………………………..
to form
ATP
oxygen
…………………………….
.
water
[13]
Below is a diagram of a mitochondrion
a)
Add labels where indicated.
[5]
matrix
cristae
b) any point on the
inner membrane
outer membrane
inner membrane
intermembrane space
b)
Indicate on the diagram the precise site of the electron transport
chain
[1]
An experiment was carried out to measure the rate at which a sample of mitochondria used
oxygen under different conditions.
The mitochondria were placed in a well oxygenated liquid with a water potential equal to the
water potential of their contents.
At time A, an end-product of glycolysis was added to the liquid. At times B, C and D, ADP was
added.
The same amount of ADP was added each time.
The results of this experiment are shown in the graph below:
Oxygen concentration in the liquid
A
B
C
D
0
2
4
Time (mins)
6
8
a) Explain why the liquid used in the experiment should
have the same water potential as the contents of the
mitochondria
…………………………………………………………………
• to ensure there is no net movement of water/osmosis
…………………………………………………………………
• that would cause a dilution/concentration of the matrix contents
…………………………………………………………………
• or damage to mitochondria/bursting of organelle
…………………………………………………………………
………………………………………
[2]
b) (i) State the name of the substance that was added at A
pyruvate/pyruvic acid
………………………………………………………………
[1]
(ii) Name the two stages of the respiratory process that
take place in the mitochondria
……………………………………………………………
link reaction; Kreb’s cycle; ETC; oxidative phosphorylation
………………………………………………………….
[2]
(iii) State the role of oxygen in these respiratory
processes
………………………………………………………………
to reoxidise the last substance/last cytochrome in the ETC
……………………………………………………..……….
[1]
c) Explain the result of adding ADP at the following points on the graph;
(i) B and C
……………………………………………………………………………
• oxidative phosphorylation can occur/ADP converted to ATP
• which requires oxygen
……………………………………………………………………………
• to react with hydrogen to form water
• less occurs at C than B because amount of reduced coenzymes is less/ORA
……………………………………………………………………………
Oxygen concentration in
the liquid
………………………………………………………………………..…
[3]
A
B
C
D
0
2
4
Time (mins)
6
8
(ii) D
..............................................................................................................
• no reaction occurs
• due to lack of reduced NAD/FAD
• which means lack of hydrogen ions/electrons for ETC
……………………………………………………………………..………
[2]
B
Oxygen concentration in
the liquid
A
C
D
0
2
4
Time (mins)
6
8
Yeast cells can respire anaerobically using glucose as a substrate.
(i) State the end products formed from the glucose if oxygen is not available to the yeast
cells
• ethanol/ethanal
………………………………………………………………………………………………
• carbon dioxide
………………………………………………………………………………………………
[2]
(ii) Explain why ADP is required in anaerobic conditions
• ………………………………………………………………………………………………
to form ATP
• ………………………………………………………………………………………………
because glycolysis occurs
• that requires additional ADP
• ………………………………………………………………………………………………
to give a net gain of 2 ATP molecules
………………………………………………………………………………………………
[3]